Noninvasive intra-partum, or electronic fetal monitoring (EFM), is a generally accepted standard of care in obstetrics. EFM provides a visual continuous beat-to-beat recording of the fetal heart rate and a recording of uterine activity. EFM shows how the fetus responds before, during, and after each contraction and provides a graphic record for review. The goal of electronic fetal monitoring is to assist in identifying possible problems of the fetus in order to reduce or relieve that distress. The device used for EFM is a cardiotocograph, and it usually consists of two sensors placed on the mother's abdomen and held in place with a strap or belt. One sensor, the tocodynamometer (TOCO) sensor, is a pressure-sensitive contraction transducer, and measures the intensity and duration of uterine contractions during labor. The other sensor measures fetal heart rate using doppler ultrasound to detect motion of the fetal heart valves. An example of a monitor that utilizes these sensors is the Avalon fm20 manufactured by Philips (Philips Medical, Andover Mass.).
Uterine activity is measured noninvasively using a tocodynamometer (TOCO) sensor placed on the abdomen of the mother, usually fixated to the skin by a band around the belly. The TOCO sensor includes a probe that extends from the base of the sensor into the mother's abdomen. The probe is connected to a force or pressure sensor that measures how much force the tissue beneath the probe exerts on the probe. As the uterus contracts during labor, the tissue beneath the probe hardens and more force is exerted on the probe. The measured force is scaled to indicate uterine activity (UA) by the electronic fetal monitor. The monitor includes capability to adjust for differences in the baseline UA signal to compensate for band tightness and for softness of the tissue below the UA sensor. The UA signal is plotted over time and clinicians are trained to interpret the relative intensity of uterine contractions relative to prior contractions and to disregard the absolute UA value. The UA signal may be interpreted to assess several factors, such as the frequency of contractions, the duration of contractions, the intensity of the contractions (determined by the pressure sensor), and the resting tone of the uterus between contractions.
Clinicians commonly train for obstetrical procedures, such as EFM, using simulation. EFM is a key part of clinicians' training. In most training systems, the electronic fetal monitoring is simulated using a computer screen that is programmed to look like an EFM plot, rather than using an actual EFM monitor. Thus, clinicians are not able to practice using the EFM sensors that they will use on patients. Clinicians are not able to practice placement of the sensors, or any use of the actual device.
Consequently, there is a long felt need for a technology that could more accurately simulate the clinical experience of using EFM. For example, of the EFM signals could be physically simulated so that simulated uterine activity and fetal heart rate data could be presented on actual EFM devices, the realism of the simulation-based training would be improved and the clinicians in training would be able to learn to better interact with actual clinical monitors and devices during simulated crisis situations.